1. Field of the Invention
The present invention generally relates to semiconductor devices and methods for manufacturing the same. More particularly, the present invention relates to a semiconductor device in which a fluorine-containing layer is formed within a source/drain region.
2. Description of the Prior Art
As semiconductor processes advance to very deep sub-micron geometries, such as 20-nm node and beyond, and with the progress of device miniaturization, junction resistance between semiconductors and external contacts has become a critical issue; therefore, there is a strong need to invent a semiconductor device with relatively low junction resistance.
In a conventional method for manufacturing a contact, in order to reduce resistance, a self-aligned silicide (salicide) process is utilized to form a metal silicide layer on the junction between a metal contact and an active area. For example, a semiconductor substrate having at least a semiconductor device, such as a metal-oxide-semiconductor field effect transistor (MOSFET), is provided. Then, at least a metal film is disposed conformally along the entire surface of the semiconductor device so that at least a portion of the metal film can contact with source/drain regions of the semiconductor device directly. In a next step, a first anneal process is carried out to diffuse metal elements from the metal film into the source/drain regions or to pull up silicon element from the source/drain regions and a metal silicide layer is therefore formed on the surface of the source/drain regions. Then, remaining metal film is removed followed by performing a second anneal process. During this second anneal process, the resistivity of the metal silicide layers can be further reduced. Subsequently, an interlayer dielectric (ILD) having a plurality of contact holes is formed to cover the semiconductor device. The contact holes may expose a portion of the source/drain regions from the ILD. Finally, a barrier layer and a conductive layer are deposited inside the contact holes to thereby complete a semiconductor device with metal silicide contact structure. During the above-saying procedures where metal elements diffuse into source/region regions, however, metal elements inside the metal silicide layers may often not only diffuse into the interface between the metal film and the semiconductor substrate but also laterally diffuse into a region under a gate structure. Defects caused by this phenomenon include piping defects, spike defects or the like, which may incur unwanted current leakage and no doubt decrease the reliability of the semiconductor device.
Regarding the drawbacks described above, there is always a continuing need to develop a semiconductor device and a manufacturing method of the same, which has relatively high reliability and may overcome current leakage problems resulting from piping defects.